In 1961 German zoologist Herwart Bohlken suggested that the kouprey might be a hybrid population of the banteng and zebu because of similarities between the animals' skulls.

Galbreath and his colleagues tested that hypothesis in a 2006 Journal of Zoology study by comparing kouprey and banteng mtDNA. If the hybridization hypothesis was correct, the mtDNA of both animals would be similar.

"We ran the DNA, and lo and behold, our prediction was correct," Galbreath said. "We now know that this [new study] is Murphy's law in action, but at the time it seemed very convincing."

But that December a fossil kouprey skull, described by Thai scientists Chavalit Vithayanon and Naris Bhumpakphan in 2004, came to Galbreath's attention. The skull possibly dated back to the late Pleistocene or early Holocene epoch, about 125,000 to 5,000 years ago.

"You can't have a fossil kouprey skull if the kouprey is a recent hybrid," he said.

Galbreath and his colleagues formally rescinded their previous view that the kouprey was a hybrid in the March 2007 Journal of Zoology.

Given that the kouprey was its own species after all, the question remained, how did it come to share mtDNA with the banteng?

The genetic data published by Hassanin and Ropiqet suggest that at some point in the Pleistocene, a female kouprey and a male ancestor of today's banteng mated, and that this coupling occurred at least once.